"They pass or fail you. If you win, you get your driver’s license," Yanik said.

In Arizona, a lot can happen to a driver’s vision in 12 years, Yanik said.

"I've had people come in, they can't see the big 'E,' but they’re driving," Yanik said. "For example, I had a patient that ... had literally 20/400 vision and is driving a car."

If patients shouldn’t be driving because of poor vision, Yanik will discuss the situation with them. He’ll advise them that they shouldn’t be behind the wheel. He'll note the discussion on their charts.

Yanik says he is not required to report their condition to MVD. And he's not sure he can, because of doctor-patient confidentiality.

MVD spokeswoman Cydney DeModica, however, said doctors are free to report patients with poor vision. They can do so by letter. A form is available as well, she said.

If an eye doctor reports a patient has a progressive eye disease like macular degeneration, for example, the agency can move to revoke the person’s license.

Arizona drivers must have at least 20/40 vision in one eye to drive. Drivers with 20/40 to 20/60 visual acuity are restricted to daytime hours.

Optometrist Kevin Huff is familiar with the MVD reporting form. Most of his clients have low vision. And he has reported patients with low vision to the agency. But there’s a catch, he said. Eye doctors can only do so with a patient’s consent.

With his own patients, Huff will discuss with them whether they should be driving. He’ll be persuasive if he has to. Most understand when it’s time to turn in their keys, though for many it’s not an easy choice.

"When I tell someone you can't drive, I don't just say, 'You can’t drive and now. Find your way home.'"

But if person who should give up driving refuses to do so, there's always the potential for a bad accident, Huff said.

"All it has to happen is once," he said.

And partial loss of vision doesn't mean somebody has to give up driving altogether. There are degrees of impairment, and licenses can reflect that.

A motorist, for example, might be restricted from driving at night or on the freeway. Huff said many of his patients can continue driving after being fitted with corrective lenses.

That includes the bioptic telescope — a device that attaches to top of regular prescription glasses. While the glasses give a driver a wide view of the road, Huff said, the bioptic telescope "helps them see street signs and traffic signals from a little further distance."

Arizona is one of 39 states permitting low-vision drivers to use a bioptic telescope.